What are the chances of acne to return after acutane low dose long term treatment?

It's to be expected: The full course of isotretinoin will usually keep acne at bay for a year or two. It will return eventually unless the time has come for it to remit on its own. (Mine did this at age 50). I can't recommend intermittent isotretinoin; there are regimens that are milder. Since you're female, topical benzoyl peroxide plus spironolactone is one of many possibilities. Best wishes.